Journal of Volcanology and Geothermal Research 333–334 (2017) 134–144 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores Methods for mapping and monitoring global glaciovolcanism Aaron Curtis ⁎, Philip Kyle Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM, USA article info abstract Article history: The most deadly (Nevado del Ruiz, 1985) and the most costly (Eyjafjallajökull, 2010) eruptions of the last Received 12 September 2016 100 years were both glaciovolcanic. Considering its great importance to studies of volcanic hazards, global cli- Received in revised form 12 January 2017 mate, and even astrobiology, the global distribution of glaciovolcanism is insufficiently understood. We present Accepted 19 January 2017 and assess three algorithms for mapping, monitoring, and predicting likely centers of glaciovolcanic activity Available online 24 January 2017 worldwide. Each algorithm intersects buffer zones representing known Holocene-active volcanic centers with Keywords: existing datasets of snow, ice, and permafrost. Two detection algorithms, RGGA and PZGA, are simple spatial Glaciovolcanism join operations computed from the Randolph Glacier Inventory and the Permafrost Zonation Index, respectively. Remote sensing The third, MDGA, is an algorithm run on all 15 available years of the MOD10A2 weekly snow cover product from Cryosphere the Terra MODIS satellite radiometer. Shortcomings and advantages of the three methods are discussed, includ- Volcanoes ing previously unreported blunders in the MOD10A2 dataset. Comparison of the results leads to an effective ap- proach for integrating the three methods. We show that 20.4% of known Holocene volcanic centers host glaciers or areas of permanent snow. A further 10.9% potentially interact with permafrost. MDGA and PZGA do not rely on any human input, rendering them useful for investigations of change over time. An intermediate step in MDGA involves estimating the snow-covered area at every Holocene volcanic center. These estimations can be updated weekly with no human intervention. To investigate the feasibility of an auto- matic ice-loss alert system, we consider three examples of glaciovolcanism in the MDGA weekly dataset. We also discuss the potential use of PZGA to model past and future glaciovolcanism based on global circulation model out- puts. Combined, the three algorithms provide an automated system for understanding the geographic and tem- poral patterns of global glaciovolcanism which should be of use for hazard assessment, the search for extreme microbiomes, climate models, and implementation of ice-cover-based volcano monitoring systems. © 2017 Elsevier B.V. All rights reserved. 1. Introduction the latter, we must learn its global distribution and extent on our planet, and begin to address how that distribution changes over time. When volcanic systems interact with the cryosphere, a host of signif- Glaciovolcanism, in the broad sense, includes any process whereby icant outcomes result. Human communities become threatened by volcanic and geothermal systems contact four types of ice masses: phreatomagmatic eruptions, lahars (volcanic mud flows), jökulhlaups snowfields, glaciers, ice sheets, and permafrost (Smellie and Edwards, (glacial outburst floods), and a range of other hazards (Major and 2016). Direct human access to locations of glaciovolcanism is logistically Newhall, 1989). A glaciovolcanic lahar from Nevado del Ruiz volcano difficult and hazardous, leading to the obscurity of certain important killed 23,000 in 1985 (Pierson et al., 1990), and phreatomagmatic phenomena. Warm gasses leaking from flanks and summits of snow plumes from Eyjafjallajökull led to flight cancellations costing airlines and ice-clad volcanoes can form fumarolic ice caves, fumarolic ice as much as 3.3 billion euros (Mazzocchi et al., 2010). Glaciovolcanic pro- towers, and ice subsidence cauldrons. Such features are rarely studied, cesses leave a distinctive geological record containing paleoclimate in- but examples at Erebus (Curtis and Kyle, 2011; Curtis, 2015), Melbourne formation (Edwards et al., 2010). Volcanic degassing beneath thin ice (Keys et al., 1983), Hood, Rainier (Zimbelman et al., 2000), Wrangell, also produces a unique set of ephemeral ice landforms, which can sup- and Baker (Kiver, 1978) suggest such modes of glaciovolcanism may port unusual microbiomes (Connell and Staudigel, 2013; Tebo et al., be globally widespread, but largely undiscovered or unreported, leading 2015; Soo et al., 2009). Thus, glaciovolcanism provides a library of infor- to apparent rarity. Necessarily sparse, “boots on the ground” investiga- mation, but also presents a danger. To access the former and mitigate tions of these often ephemeral phenomena should be complemented and targeted using worldwide assessments of glaciovolcanism. In recent years, rich datasets regarding the distribution of the above ⁎ Corresponding author. four ice types on Earth have become available. The MODIS instrument E-mail address: [email protected] (A. Curtis). aboard NASA's Terra satellite provides a record of weekly (8-day) global http://dx.doi.org/10.1016/j.jvolgeores.2017.01.017 0377-0273/© 2017 Elsevier B.V. All rights reserved. A. Curtis, P. Kyle / Journal of Volcanology and Geothermal Research 333–334 (2017) 134–144 135 snow cover at 500 m spatial resolution extending back to 2000: the the literature. Many studied Type 2 deposits date to the Last Glacial MOD10A2 product (Hall et al., 2006). The Randolph Glacier Inventory Maximum. Type 1 is common at alpine volcanoes but is only rarely rec- (RGI), a “globally complete” catalog of glaciers, was compiled by ognizable in the geological record. Tuffen and Castro (2009) described Pfeffer et al. (2014). Ice within the soil is more difficult to map; it is the first discovery of an eruption deposit demonstrably formed beneath not observable by remote sensing alone. Using elevation data and global “thin” ice, “only 35–55 m thick.” Eruption into such snowpacks at air temperature data from general circulation models (GCM), Gruber Fimmvörðuháls and Tolbachick were recently observed in situ by (2012) was able to create a high-resolution model called the Permafrost Edwards et al. (2012, 2014).Alpinefirn fields and thin glaciers respond Zonation Index (PZI) which provides an estimate of frozen ground ex- not only to eruption of lava, but also undergo significant melting and de- tent worldwide. In the Northern Hemisphere, PZI closely matches the formation in response to fumarolic activity and flank degassing. Loss of commonly used Circum-Arctic Map of Permafrost and Ground-Ice Con- alpine ice masses in response to increased degassing can be an early in- ditions (Brown et al., 1997), and it was validated for use in the dicator of volcanic unrest (Bleick et al., 2013; Kiver, 1978). In some arid Himalayas by Schmid et al. (2015) and in New Zealand by Sattler et al. environments, galciovolcanism is the only process capable of supplying (2016). Many decades of field investigation provide good constraints water to biological communities and for aqueous mineral processes on the locations of volcanic centers active during the Holocene. The such as weathering. This primarily occurs at Type 1 systems like Mt. Er- best catalog is the Smithsonian Institution's Volcanoes of the World ebus, Antarctica, where fumarolic degassing not only produces liquid (VOTW) database, which contains entries for 1443 terrestrial volcanoes water but also melts caves into the summit caldera ice mass. Native mi- (and 113 seamounts) (Global Volcanism Program, 2013). crobiological ecosystems with unusual metabolic strategies and molec- Before these datasets were available, no global map of ular machinery have recently been identified in the caves (Connell and glaciovolcanism existed, although compilations of case studies such as Staudigel, 2013; Tebo et al., 2015). Firn caves in the summit crater of Major and Newhall (1989) did exist. Curtis (2014) produced a prelimi- Mount Rainier are also likely to host a microbiome. “Warm ground” nary global map using MOD10A2 data. In 2015 and 2016, worldwide areas occur when volcanic heating melts holes in the ice cover, maps were published, but lacked description of the methods used to supporting patches of moss in the otherwise inhospitable Antarctic create them. Fig. 1 of Waitt et al. (2015) cites the use of GLIMS (Global (Broady et al., 1987; Soo et al., 2009). These ecosystems depend on Land Ice Measurements from Space) polygon data, but displays ice- the water, consistently warm microclimate, and UV protection in the clad volcanoes in areas (e.g. Aleutian Islands) where no GLIMS polygons case of caves, all of which are available due to glaciovolcanism. exist. Presumably, the spatial analysis was manually augmented based The remaining category of glaciovolcanic processes, Type 3, occurs on expert knowledge. Smellie and Edwards (2016) include similar when magma bodies and related hydrothermal and volcanic systems maps, but they must be considered illustrative schematics rather than encounter permafrost. This may be the primary glaciovolcanic phenom- quantitative global surveys as they are presented without a description enon in the geologic history of Mars, where the major water reservoir is of input data or cartographic methods. In an effort to produce a system- known as the cryolithosphere, a permafrost-like layer which is thought atic global